The present invention relates to a damper which allows a predetermined degree of movement before damping action is instituted.
Dampers are employed in a variety of applications for preventing excessive, uncontrolled movement. In one application, for example, in horizontal or vertical axis washing machines, designed dampers are employed to prevent the washer basket from over-vibration during a spin cycle. U.S. Publication No. 2003/0183994 entitled DAMPER SPRING STRUT, published Oct. 2, 2003, discloses the environment of such an application for a damper.
Each time a conventional damper is employed, for example, in a washing machine, and subjected to loads during an unbalanced spin cycle, the damping action reduces the energy available for the spinning action and, therefore, robs energy from the overall system operation. Damping action also transmits forces to the floor, which can result in unwanted noise and household vibration. In order to allow a certain amount of unobjectionable vibration during such a spin cycle, a damper has been proposed as disclosed in U.S. Publication No. 2006/0054440 entitled DAMPER, published Mar. 16, 2006, the disclosure of which is incorporated herein by reference. This damper, although providing some free motion before damping action occurs and, therefore, is energy saving, is relatively large, and requires a considerable amount of space in the damping device itself for its effective operation.
There remains a need, therefore, for a compact free space damper which allows a minimum amount of motion without providing damping action but, once that threshold has been exceeded, provides the desired damping for the application in which the damper is employed. Additionally, there remains a need for a damper which is gradually engaged through cushioning structure to smooth the transition between undamped and damped operation.